Dust filtration system

ABSTRACT

A vacuum cleaning or loading device of the type including a means for filtering airborne fine particulate material also includes a back-up filter system for protecting the vacuum exhauster or blower. A by-pass system may preferably be used with the back-up filtration system to protect the primary filter media when the cleaner or loader is being used for collection of liquids. The device may be self-propelled or stationary and may be used for various collecting, loading, transportation or cleaning jobs.

United States Patent 11 1 Moore, Jr. et al.

[451 May 27, 1975 1 DUST FILTRATION SYSTEM [75] Inventors: Lionel G.Moore, Jr.; Thomas P.

Flynn, both of Milwaukee, Wis.

[73] Assignee: Super Products Corporation,

Milwaukee, Wis.

22 Filed; Jan. 10, 1974 21 Appl. No.: 432,243

[521 U.S. Cl. 55/314; 55/319; 55/341;

55/350; 55/419 [51] Int. Cl B0111 46/44 [58] Field of Search 55/309,312, 314, 315,

[56] References Cited UNITED STATES PATENTS 2,657,416 11/1953 Smith15/353 X 3,406,423 10/1968 Young 15/347 x 3,541,631 11/1970 Kluge et a115/352 X 3,587,130 6/1971 Young 15/352 FOREIGN PATENTS OR APPLICATIONS903,890 12/1953 Germany 55/418 Primary Examiner-Frank W. LutterAssistant Examiner-David L. Lacey [57] ABSTRACT A vacuum cleaning orloading device of the type including a means for filtering airborne fineparticulate material also includes a back-up filter system forprotecting the vacuum exhauster or blower, A by-pass system maypreferably be used with the back-up filtration system to protect theprimary filter media when the cleaner or loader is being used forcollection of liquids. The device may be self-propelled or stationaryand may be used for various collecting, loading, transportation orcleaning jobsv 7 Claims, 5 Drawing Figures PATENTEUMMY ms 3,885,932

SHEET 1 Pmmmmv 1915 3.885932 SHEET 2 [JUST FILTRATION SYSTEM BACKGROUNDOF THE INVENTION This invention pertains generally to the art ofindustrial vacuum loaders or cleaners. Such machines have becomeincreasingly important in recent years because they allow their users toincrease efficiency of their op erations by conserving valuablematerials, by reducing labor costs and by simultaneously providingcleaner and safer work environments. Such machines are commonly employedin foundries, mines, grain storage vessels, primary metals plants,minerals processing plants, municipal streets and other areas whereloose materials should desirably be collected, either to recover theireconomic value or for purposes of cleanliness and safety. The increasedinterest in machines of this type has been accompanied by acorresponding development of the technology involved in theirconstruction. Early machines, typified by leaf pick-up vehicles,employed a fan through which debris passed during collection. Latermodels employed exhasut type vacuum fans to suck debris through anintake hose and deposit it in a collection hopper without debris passingthrough the fan. Screens were sometimes employed to protect the fans,and some machines sprayed water into the air stream to remove entrainedparticles. Still more advanced models have employed multistagecentrifugal blowers in place of single stage fans.

One known system for loading and cleaning, using such a centrifugalpump, utilizes a flexible vacuum intake hose for conveying refuse orother material into a main collection hopper. [n such a system, thevacuum blower or exhauster is separated from the main hopper by afiltration means for protecting the vacuum blower from fine dustparticles which may become entrained in the air stream flowing throughthe system. One known means for filtering dust particles utilizes filterbags for collecting the dust and reverse air flushing for periodicallycleaning the filter bags. The basic principles of this type of filterare disclosed in US. Reissue Pat. No. 24,954 for an Apparatus forFiltering Solids from Gas-Solid Suspensions issued May 28, 196]. Another filtration system utilizes a fabric filter media stretched over aplurality of parallel bars to form a continuous series of bags. Arepresentative system of this type is described in US. Pat. No.3,l86,02l for Power Sweeper," issued June l, 1965 to Krier et al. TheKrier el al bags are cleaned by shaking the parallel bars to removeaccumulated dust. Yet another filtering arrangement provides openbottomed bags which are pulsed with blasts of compressed air to expandthe bags and flake off dust accumulations.

The filtering devices discussed above may be used in a variety ofindustrial operations such as vacuum cleaning of debris from fatories orfoundries, street cleaning, loading or conveying of wheat and othergrains, leaf pick-up etc. One problem which is frequently encounteredwith the prior vacuum cleaners and loaders is that the fan is damaged ifthe filtration system fails thereby allowing large amounts of dust topass into the fan. This problem is compounded if positive displacementpumps are used in place of vacuum pumps. Positive displacement pumps areadvantageously employed in large vacuum machines because they possessincreased efficiency over centrifugal fans and fuel consumption forpositive displacement pumps is as much as 50% of that required bycentrifugal pumps. In addition, velocity and vacuum control can be moreprecise using positive displacement pumps. The difficulty up until now,however, has been that positive displacement pumps are much moresusceptible to damage if filter bags fail and large amounts of dust areallowed to enter the pump.

Another problem with prior devices arises when a single machine is usedto collect or load both solids and liquids. During the collection ofliquid materials, the filtering media usually becomes damp. and uponswitching the unit for collection of solid materials, airborne dust canform a cement-like cake on the filter. The cake cannot be removed by thenormal cleaning procedure. On proposed solution to this latter problemhas been to bypass the filtering media when liquids are collected. Thismay be accomplished by providing a manually operated switching device,and the machine operator makes whatever adjustments are necessarydepending on the current use of the machine. Any error in judgment onthe part of the operator could quickly result in vacuum pump damage.Because of the relatively high expense involved in the purchase of largevacuum loaders and cleaners of this type, downtime occasioned by theneed to replace the filtering media or to repair or replace the vacuumpump can be costly.

A still further problem with the prior art filtration units is that theyare relatively inflexible and are usually designed for a specificmachine, i.e., one mounted on a truck chassis or one designed forstationary units. Those who may need filters for several types of vacuumunits would then need to purchase several different filtration units,whereas such would not be the case if the filtering system were adaptedto be readily connected to different vacuum cleaners and loaders.

SUMMARY OF THE INVENTION It is a primary object of this invention toprovide a bag filtration housing including both a primary filtra tionmeans and a backup filtration means for fan or vacuum pump protection.

It is another object of the invention to provide a filtration system forvacuum cleaners and loaders including a bypass arrangement for directingthe air stream around the primary filtration means directly to asecondary or back-up filtration means.

It is yet another object of the invention to provide a filtration systemwhich is readily adaptable to existing vacuum loaders and cleaners ofboth the mobile and stationary types.

It is a further object of the invention to provide a filtration meansfor industrial vacuum loaders and clean ers having increased filterlifetime.

It is yet a further object of the invention to provide a filtrationmeans for industrial vacuum cleaners and loaders including an easilymanipulated switching mechanism, operable when a single unit is to beused for collection of both liquid materials and solid materials.

A still further object of the invention is to provide an industrialvacuum loader and cleaner including afloat control mechanism forpreventing blower of filter damage caused by overloading of the maincollection hopper when liquids are being collected.

How these and other more specific objects of the present invention areaccomplished will be described in the following more detaileddescription of a preferred embodiment of the invention taken inconjunction with the drawings. Generally, however, the inventionincludes a filtration housing divided into chambers which are soarranged that the vacuum air stream may selectively be passed througheither a primary and a secondary filtration system or only through thesecondary fil' tration system. In a preferred embodiment of theinvention, a series of tubular fabric filter bags are used as thefiltration media in both the primary and secondary filtration chambers.but the secondary filtration bags have a larger average pore size thanthose of the primary filter bags. A reverse air flushing system ispreferably used in conjunction with all the tubular fabric filter bagsfor periodically cleaning the exterior bag sur faces of accumulateddust. Such cleaning of the exterior bag surfaces may be accomplishedautomatically. A quick switching means is also preferably employed toenable selection of air flow paths through the housing. In the firstpath, air travels through the primary filtra tion bags, through a plenumabove the primary filtration bags. down a connecting passageway and upthrough secondary filter bags, while in the second path, air passesdirectly to the secondary filter bags. A float mechanism is alsopreferably employed when the ma chine is being used for collectingliquids to prevent the liquid from entering the filter housing or theblower. The embodiment to be described in detail below may be adaptedfor industrial cleaning and loading in either stationary or mobile modesof operation.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of a preferred filterhousing according to the present invention showing generally thelocation of the filter bags and the multi-chamber arrangement;

FIG. 2 is a vertical section through the line A-A of the filter housingof FIG. I together with main collec tion hopper and illustrating airflow in the solid collection mode of operation;

FIG. 3 is similar to FIG. 2 and is a side vertical section through theline BB of FIG. 1 showing the main collection chamber in conjunctionwith the housing shown in FIG. 1, but illustrating the liquid collectionmode of operation;

FIG. 4 is a cut-away oblique view of the housing illustrated in FIG. 1showing the construction of the by-pass duct and the primary andsecondary filter chambers of FIGS. 1-3; and

FIG. 5 is a rear sectional view taken along the line CC of FIG. 2showing the orientation of the filter bags and the by-pass duct.

DESCRIPTION OF A PREFERRED EMBODIMENT Because of the unusual design ofthe filtration bag housing of the present invention, it is difficult todescribe the housing with reference to a single figure, and,accordingly, reference will simultaneously be made to FIGS. 1-5. FIG. 1is a top view ofa filter housing shown to include a front wall 12, rearwall 14, side walls 16 and bottom 13 (not shown). While these walls areshown to be reinforced sheet metal in the drawings, any known materialsfor constructing flat walled vacuum chambers of large size may beemployed. Housing 10 is a generally rectangular box. The front and rearnotations used in the description of the preferred embodiment will bemore fully understood by reference to FIGS. 2 and 3 wherein housing 10is located generally in front of (and to the left of in the drawings) amain collection chamber 65, the air flow being from the main collectionchamber 65 through housing 10, through a connecting hose 169 to a vacuumpump I70, and out an exhaust stack 171. Proceeding generally from therear wall 14 to the front wall 12, housing 10 is generally divided intofour sections by a series of vertical partitions. The first section 15contains the intake passageways 17 and 18 (See FIGS. 2 and 3). Thesecond section is the primary filter section 30. The third section is apassageway 40 in front of the primary section 30. The fourth section isthe secondary filtration section 60.

Section 15 is vertically divided into two passageways extending from thetop of housing 10 down towards the bottom of housing 10 by alongitudinal partition 28. Passageway I7 terminates in an opening 19into the primary filter section 30. The other passageway 18 of chamber15 defines a passageway from the top portion of the housing 10 down to abypass duct 20 which passes longitudinally below main filter section 30and into the secondary filtration section 60. A metal plate 23 havingopenings 24 and 25 is welded or otherwise attached transversely over thetop of the first section 15. Opening 24 leads to passageway 17, whileopening 25 leads to passageway 18. The opening 19 of passageway 17 intothe primary filtration chamber 30 can be seen in FIG. 2, while theopening 56 0f the by-pass duct 20 into the secondary filtration chamberis shown in FIG. 3.

The bottom of the main collection section 30 is formed generally in theshape of an inverted pyramid by bottom walls 32 which define areceptacle 31 for the dust collected in section 30. An opening 34 isprovided at the bottom of the inverted pyramid for removal of collectedmaterial. It has been determined that a steep incline of walls 32 allowsa greater percentage of material to collect in receptacle 31. Apreferred angle would be approximately 60. Main collection chamber 30 isfurther defined by a rear wall 33, a front wall 39 and side walls 16 ofunit 10. Wall 33 serves to divide sections 15 and 30 and is disposedfrom the top of unit 10 down toward the bottom 13 to define opening 19(FIG. 2). Wall 39, on the other hand, extends from the bottom 13 ofhousing 10 to a location somewhat below its top, and suitable openings21 are provided in walls 33 and 39 for the by-pass duct 20.

A plate member 38 having opening 36 for receiving the primary filters iswelded to the four vertical walls of chamber 30 at a location generallysomewhat below the top of housing 10. The forward side of plate 38 isattached to the top of wall 39.

Parallel to, and forward of Wall 39, is another vertically extendingwall 41 secured between side walls 16. Wall 41 extends from the top ofunit 10 downwardly to a point above bottom 13. Transverse walls 39 and41 and side walls 16 then define section 40. Wall 41 terminates at itslower end at opening 52 of section 40 into section 60.

Surrounding section 30 and 40, and attached to walls 36, 41 and sidewalls 16 is an inwardly directed horizontal flange 43 which serves, aswill be more fully understood below, as a securing surface for cover 44which in turn defines the plenum 45 above the primary filters andpassageway 40. A similar horizontal flange 46 is provided between wall41, front wall 12 and side walls 16 for attachment of a cover 48 for thesecondary filtration chamber 60. Hinges 42 may be used to secure covers44 and 48 to the top of the filter housing.

Finally, with reference to FIGS. 1 and 3, a horizontal plate 58 iswelded or otherwise attached across section 60 somewhat below the levelof cover 48 and generally coplanar with plate 38 covering section 30.Plate 58, like plate 38, is provided with openings 57 for mounting thesecondary filters. The area between cover 48 and plate 58 defines thesecondary filter plenum 56. A duct 63 passes through front wall 12 ofunit from plenum 56, leading to the fan or vacuum pump through hose 169,as will be more fully understood shortly hereafter. Unit 10 then is agenerally enclosed rectangular box having inlet openings 24 and 25 andan outlet opening 63.

Referring now to FIGS. 2 and 3, housing 10 of FIG. 1 is shown connectedto a main collection chamber 65. Collection chamber 65 may be arectangular chamber defined by rear door 66, front wall 67, bottom 68and top 69. The side walls are not shown. As discussed above inconnection with the construction of housing 10, chamber 65 also may beconstructed of reinforced sheet metal or other materials suitable forflat-walled vacuum chambers. The vacuum in chamber 65 may be in therange of 10-20 inches of mercury, and one skilled in the art couldreadily select the proper construction materials.

Located rearwardly of chamber 65 is a flexible hose 73 which may be ofany desired length or configuration for being positioned above thematerial to be drawn into chamber 65. Hose 73 is attached through therear of chamber 65 by means of a gasketed seal 74. Other openings suchas 74' may be provided at other locations on chamber 65 for allowinggreater flexibility in hose attachment. lf opening 74' were to be used,opening 74 could be closed with a suitable cover, or in some instances,both openings could be employed simultaneously.

Rear door 66 is preferably pivotally attached to top 69 by a hinge 76 soas to allow opening of the door for debris removal. The particularconfiguration of the chamber, access door and hose form no part of thepresent invention and other modifications known to the art can be used.For example, if the entire unit is to be used for loading rather thandebris collection, chamber 65 could be supplied with a conveyor means inbottom wall 68 for continuously transporting the material sucked intothe chamber to a central collection site, a truck or a conveyor belt.Pneumatic or screw conveyors are examples of such modifications. Also,if a high degree of separation in chamber 65 is desired, the entirechamber could be replaced by a centrifugal separator, which separatorcould also be equipped with a transport or conveyor means. A properlydesigned centrifugal separator would allow a greater percentage ofparticulate material to be retained in chamber 65.

FIG. 2 also shows a hoist 78 pivotally mounted to top wall 69. Hoist 78may perform several functions. A hook 71 of hoist 78 is designed forbeing secured to a bracket 72 on hose 73 or to a bracket 77 on rear door66. By selectively attaching the hoist to one of the brackets, hoist 78can be used to mainpulate hose 73 or to open rear door 66. A latch means75 which is exteriorly mounted to bottom 68 of chamber 65 serves to lockrear door 66 to the top, bottom and side walls of chamber 65. Suitablegasket means, (not shown) can also be used to insure a vacuum tight sealbetween the pivotably mounted door and the remainder of chamber 65.

The manner of connecting chamber 65 to housing It) will now bedescribed. While the particular embodiment shown in FIGS. [-3 providesthe capability of selecting the flow path of the vacuum air stream bymanipulations performed in chamber 65, other means for selecting theflow path could also be used. The top area of chamber 65 adjacent thefront wall 67 is divided into two longitudinal passageways leading to adownwardly directed extension 80 of top wall 69, and selection means areprovided internally of chamber 65. Extension 80 terminates in arectangular surface 82 which mates with surface 23 surrounding theopenings to bag housing 10. A gasket 81 insures an air-tight sealbetween housing 10 and chamber 65. The combination is so designed thatthe openings of the housing mate with the passageways of the chamber,even after tilting the chamber as will be later described. Any othersuitable connecting means may be employed between chamber 65 and housing10. For example, if chamber 65 is to be separated from housing 10, aflexible hose could be provided in place of the connecting means shownin the figures. A first longitudinal passageway 84 at the top of chamber65 is defined by the top wall 69, the remote side wall and a horizontalwall 85 and opens into the interior of chamber 65 through opening 86.This passageway serves to connect the interior of chamber 65 to opening24 of housing 10 when solid material is being collected in chamber 65.Opening 86 may be closed by a cover 89 which is pivotally attached tobracket 88. The other end of cover 89 can be secured to bracket 87 whenliquids are being collected. Gaskets (not shown) can be provided toinsure an air-tight seal when cover 89 is secured between brackets 87and 88 thereby closing opening 86.

The second longitudinal passageway 92 (FIG. 3) leads to opening 25 ofhousing 10 and is employed when liquids are being collected. Passageway92 is defined by top wall 69, the near side wall of chamber 65 and avertical wall 94. Opening into passageway 92 is another verticalpassageway 93 extending up along front wall 67 from a float chamber 95attached to front wall 67. Vertical wall 94 extends downwardly from thetop of chamber 65 to a point above float chamber 95, thereby definingpassageway 92. Within chamber 95, which is open at its lower end, is afloat 96 having a rod 97 connected through an opening 98 of chamber 95to a cover plate 100 by hinge 101. When liquids are being collected,cover plate 100 is generally horizontal as shown in FIG. 3 and float 96is located at the bottom of its retaining chamber 95. Cover 100 ishinged adjacent the front wall 67 by hinge 102. As liquids reach apredetermined height in chamber 65, the float 96 will begin to rise, atthe same time raising the interior end of cover 100 so that itapproaches the lower end of wall 94. When cover 100 nears the lower endof wall 94, the air stream flow through passageway 93 aids in completeclosure of the passageway and prevents liquid from entering thepassageway. Cover 100 is mechanically locked to the lower end of wall 94when solids are being collected. Any other suitable float or valvearrangement may be employed to prevent liquids from entering the filterbag housing.

Although the preferred embodiment of the invention described inconnection with the figures shows covers 89 and 100 as the only meansfor selecting the flow paths into either openings 24 and 25, any othersuitable means can be employed. For example, instead of providing twoseparate passageways having extension 80, a single passageway from theinterior of chamber 65 could be connected directly to plate 23 ofhousing and means could be provided on housing 10 for selec tivelyclosing openings 24 and 25. This could be accomplished by providing ahinged cover between the openings. The advantage of the preferredsystem, how ever, is that selection of the air stream flow path can beaccomplished without separating extension 80 from plate 23.

In the illustrative embodiment of FIGS. 2 and 3, means are shown forelevating the front of chamber 65 for discharging collected materialthrough rear door 66. FIGS. 2 and 3 show the bag housing 10 and cham ber65 in a stationary environment and supported on piers 105 which may beconstructed of concrete or steel. Housing 10 is attached to support pier105 by bolts 106, while chamber 65 is pivotally supported at itsrearward end by a pair of mating brackets 90. Located intermediate theends of bottom wall 68 of chamber 65 is a bracket 108 mounted to bottom68. A hydraulic jack 110 is rotatably mounted to bracket 108 and also toa bracket 109 on an adjacent support pier 105. The hydraulic cylinderand brackets are so arranged that upon extension of the piston 11] ofhydraulic cylinder 110, by application of power from a by draulic fluidsource (not shown), the forward end of chamber 65 will be elevated tofacilitate removal of collected material. Other suitable means forelevating the forward end of chamber 65 can be used, such as, forexample, screw or hydraulic jacks. The arrangement using support piersis illustrative and different means can be employed if chamber 65 andhousing 10 are to be mobile, i.e., mounted on a tractor or truckchassis. Examples of elevating means for truck mounted chambers are wellknown to the art, i.e., those used for dump trucks, garbage collectingvehicles, etc.

Reference is now made to the bag housing 10 for a description of thefiltration system of the illustrated embodiment. Tubular fabric filterbags 120 are supported by plate 38 in the primary filter section 30.Bags 120 are themselves internally supported by a cylindrical wire frame121 to prevent bag collapse under vacuum conditions. Suspended by plate58 in the secondary filtration section 60 is a second plurality ofsimilar wire supported bags 140. Bags 120 and 140 may be identical, butin a preferred embodiment of the invention, the average pore size of thebags is different. It has been found that in order to obtainsubstantially complete dust removal under ordinary conditions an averagepore size of approximately 1 micron is required. Therefore, bags 120should be constructed of a material which has an average pore size ofapproximately I micron. Either woven or felted materials can be suitablyemployed, and a felted material with pores in the range of 0.5 to 2microns is satisfactory for most uses. On the other hand, secondaryfilter bags 140 are used, as described above, mainly to protect thevacuum pump should the primary bags fail. For this reason, it is notnecessary that bags 140 have so small a porosity. It has been found thatbags having an average porosity of approximately 10 microns are suitablefor use as the secondary bags, since particles less than approximately10 microns in size will not do significant damage to conventional vacuumpumps in the time it would take the operator to stop the machine andmake whatever repairs to the primary bags are necessary. The particularconstruction of the filter bags and the pore sizes mentioned above areillustrative only and the invention should not be limited to anyparticular filter material or pore size. It is obvious that undervarying circumstances, entirely different parameters might be selectedand for some uses a small average porosity may not be necessary at all.Therefore, the choice of the porosity for bags and is a design choice.

Each of bags 120 and 140 is held in place by a top retainer ring 123which exceeds in diamater the hole and over which the fabric of each bagis stretched. After the bags are dropped through their hole, a venturi126 is inserted into the bag opening and is in turn supported by theretainer ring. As will be apparent shortly, the venturi enhances the bagcleaning efficiency of the reverse flow air cleaning system. Securingall of the bags and venturis in place is a plurality of rotatableclamping plates 127 suitably disposed on plates 38 and 58. The center ofeach plate 127 is secured through either plate 38 or plate 58 by a bolt128, passing through its bag support plate and into a strip of metal 129welded or otherwise attached to the support plates. Should a bag ineither the primary or secondary filtration sections fail, the bag may besimply removed by loosening bolts 128 and turning the clamping plates127 so that their contacting protrusions are turned away from the bags.The venturi 126 is then removed and the bag lifted out and discarded orrepaired.

Suspended within plenums 45 and 56, as can be seen from FIGS. 2 and 3,are manifold or blow pipes and 160, respectively. Actually such pipesare suspended over each row of tubular filter bags 120 and 140 eventhough only two such pipes can be seen in the drawings. The pipesinclude holes 151 and 161, respectively, located centrally above the bagopenings. Pipes 150 and 160 pass outwardly through covers 44 and 48 ofplenums 45 and 56 and are sealed therethrough in a manner not shown.Pipes [5! and 160 terminate outside housing 10 at valves 155 and 165.Each of the other pipes suspended over the filter bags are similarlyconnected to valves 155 and 165. A continuous path then is providedbetween the hole of each pipe, the pipe itself, and the valves.Couplings 153 and 163 are provided respectively in pipes 150 and toallow for rapid disconnection of the pipes from the valves. While thefigures illustrate the valves being mounted above bag housing 10, it ispreferred that the valves be mounted through the side walls 16 ofhousing 10. This would leave covers 44 and 48 free of obstruction tofacilitate access to plenums 45 and 56 for bag repair or inspection.

The operation of the illustrated embodiment of the invention will now bedescribed, first in connection with the collection of dry material. Dustresulting from such collection passes through passageway 84 andpassageway 17 of section 15 of bag housing 10 through inlet opening 24.The flow of such air is shown in FlG. 2 to pass around flange 19 of wall33 and up to and through the walls of primary fabric bags 120. The air,then being substantially free of dust, passes through plenum 45 of theprimary bag section 30 through section 40, around flange 52 of wall 41and up to and through the walls of secondary filter bags 140. Thefiltered air then passes through the secondary bag plenum 56 and leavesthe bag housing 10 through duct 63 to the vacuum pump 170. During thecleaning or loading operation, the bag cleaning mechanism is operatedintermittently, for example, in one-tenth of a second intervals, toblast any accumulations of dirt off of bags 120 toward the opening 34for removal. The back flushing is accomplished simultaneously with thecontinuous operation of the vacuum pump so that it is unnecessary tostop the cleaning or loading operation. Fine dust particles contactingthe primary bags 120 would tend to accumulate during the intervalsbetween back flushing and form loose cakes which are easily knocked offby the pulse of back flushing air directed into the bags through holes151 of pipes 150. Should any of bags 120 fail and allow dust to passinto the primary filter plenum 44 and section 40, the major portion ofsuch dust would accumulate on the exterior surface of bags 140, and forthis reason a back flushing of that bag may also be provided in thepreferred embodiment. The secondary bag back flushing would result inthe accumulated dust being dropped to the bottom of the secondary filtersection 60 and removal of any such accumulation is accomplished throughremoval door 72 at the bottom thereof. Periodic checks by opening door72 would indicate to the operator if any failures had occurred in theprimary bags, because no accumulation should occur in the absence ofprimary bag failure. In another embodiment of the invention, thesecondary back flushing provision may be eliminated or manual backflushing of the secondary bags can be employed. As stated hereinbefore,the primary function of the secondary filter bags is protection of thevacuum pump, rather then elimination of dust discharged into theatmosphere. However, even the secondary bags would reduce some dustemissions in the event of primary bag failure.

In collecting liquids, opening 86 is closed and the cover 100 of duct 93is opened. This makes operable the by-pass system wherein the primarybags 120 would be by-passed by the air stream and would be protectedfrom the moist air passing through housing 10. The moist air would passdirectly through duct 20 to the secondary bags 140 and into secondaryplenum 56 to blower 170.

Should it later be desired to again collect dry material, the procedurejust outlined would be reversed so as to direct dust laden air into theprimary bag section 30. The flow of dust laden air would pass throughdry bags 120. It is also contemplated that by using the device shown inthe embodiment illustrated in FIGS. l-S, the flow of dry air throughhousing would quickly dry bags 140 and prevent caking on bags 140,should primary bags 120 later fail.

The compressed air source and timers for valves 155 and 165 are notshown and the detailed construction of the valve mechanism is also notshown. In the preferred embodiment of the invention, the cleaning ofindividual bags is accomplished sequentially, i.e., one row of bags iscleaned and a cyclical timer is employed to direct the cleaning blastsof air through one row at a time and then cycle the cleaning blasts tothe original row. Reference is here made to various U.S. patents whichdescribe in detail such cyclical filter bag cleaning timers. See U.S.Pat. No. 3,436,899 issued to .I. Pausch on Apr. 8, 1969 for SupersonicCleaning of Filter Media,

U.S. Pat. No. 3,541,631 issued on Nov. 24, 1970 to B.-

M. Kluge et al for Industrial Vacuum Loader and Cleaner," and U.S.Reissue Pat. No. 24,954 issued Mar. 8, I961 to H. Church forApparatusfor Filtering Solids from Gas-Solid Suspensions. The filtration systemdisclosures of these patents are hereby expressly incorporated byreference into this specification.

While the back flushing mode has been shown in the preferred embodimentof applicant's invention, other means for cleaning filters may also beemployed. Two examples of alternative filter systems are those employingbag shakers to shake accumulated dirt from the bag surfaces andunsupported bag systems which expand in a wave-like manner to flakeaccumulated dirt off of the bags.

Applicants invention is primarily directed to a bag housing which isadaptable for both mobile and station ary environments. Collectionchamber 65, bag housing 10, vacuum pump 170, etc. may be variouslyarranged and the bag housing 10 itself may be variously constructed tofit space requirements of existing vacuum loaders or cleaners. Servicingand inspection of the housing is minimized because a system is providedfor preventing blower damage should a primary filter bag 120 fail, andprimary bags 120 should have an increased lifetime since they are notinvolved in the loading or collecting of liquids into chamber 65. Acontrol panel 200 is also schematically illustrated in FIGS. 2 and 3,but the electrical connections of the panel to the various parts of themachine are not shown since the details of the electrical connectionwould be obvious to one skilled in the art. In the schematic example,six control knobs (A-F) are shown. Knob A could be connected to the tailgate latch for automatic extension of the latches to allow door 66 to beopened. Knob B could be connected to hoist 78 for hose manipulation ordoor opening, even if the chamber were not ele vated. Knob C could beused for controlling the velocity of the vacuum pump 170. As previouslydisclosed, pump 170 may be a positive displacement pump, since thepresent invention provides greater protection to enable the economicaloperation of such pumps. Knob D could control the back flushing of bagsand so that one, both or none of the bag sections are cleaned dependingon the particular cleaning or loading jobs. Finally, knobs E and F couldbe employed if a mechanical system for operation of covers 89 and 100were included. Such a system was not shown in the figures, but it shouldbe obvious to one skilled in the art that any mechanical system forclosing the openings to passageways 84 and 92 could be employed. Sowhile the invention has been described in connection with a preferredembodiment thereof, the invention is not to be limited by thatdescription, but is to be limited solely by the claims which follow.

We claim:

1. A vacuum loading or cleaning device comprising:

a material receiving chamber, said chamber including inlet means andoutlet means,

vacuum pump means connected to said chamber outlet means for creating avacuum in said chamber and for drawing a high velocity air stream fromsaid chamber inlet means through said chamber to said chamber outletmeans,

filter means interposed between said chamber and said pump means forfiltering fine particulate material from the air stream passing fromsaid chamber to said pump means, said filter means comprising: a housinghaving two inlet means coupled with said chamber outlet means and ahousing outlet means coupled to said vacuum pump means.

air stream directing means within said housing defining two air streamflow paths through said housing, one of said flow paths connecting oneof said housing inlet means to said housing outlet means and the otherof said flow paths connecting the other of said housing inlet means tosaid housing outlet means,

filters in said housing for filtering fine particulate material from theair stream passing through said housing, said filters comprising a firstand a second portion, said first portion and said second portion of saidfilters being arranged in said housing for filtering in series the airstream passing through said first flow path, said second flow pathbypassing said first portion of said filters but including said secondportion of said filters means for selectively controlling the air flowfrom said chamber outlet means to said housing outlet means through oneof said flow paths.

2. The invention set forth in claim 1 wherein said chamber outlet meanscomprise first and second outlets, said first outlet being connected tosaid one housing inlet means and said second outlet being connected tothe other of said housing inlet means, said chamber outlets beingselectively closable whereby air passing through said chamber may leavesaid chamber through only one of said chamber outlets.

3. The invention set forth in claim 2 further including first and secondduct means coupling the interior of said chamber to said first andsecond chamber outlets respectively, one end of said first duct meansbeing coupled to said first chamber outlet and the other end of saidfirst duct means being open to the upper portion of said chamberinterior, and one end of said second duct means being coupled to saidsecond chamber out let while the other end of said second duct means isopen to said chamber interior at a location therein below said other endof said first duct means.

4. The invention set forth in claim 3 wherein said second duct means isselectively closeable by a float valve means disposed at said other endof said second duct means, whereby said second duct means is closed tothe passage of air if liquid is being collected in said chamber and saidliquid reaches a predetermined height in said chamber.

5. The invention set forth in claim 4 wherein said filters comprisetubular fabric filter bags suspended within said housing so that the airstream passing through said housing flows from the exterior of said bagsto the interior of said bags and fine particulate material accumulateson the exterior surface thereof.

6. The invention set forth in claim 2 wherein said air stream directingmeans define:

a first vertical section of said housing, said first section beingdivided into first and second vertical passageways, the first one ofsaid passageways connected to said one inlet means and the second one ofsaid passageways connected to said other inlet means,

a second vertical section adjacent said first section and containingsaid first portion of said filters, said second vertical section beingconnected to said first passageway,

a third vertical section adjacent said second vertical section anddefining a third passageway leading from the upper portion of saidsecond vertical section to the lower portion of,

a fourth vertical section adjacent said third vertical section andcontaining said second portion of said filters said fourth verticalsection connected to said third passageway and said housing outlet, and

a first horizontal passageway passing through and beneath said secondvertical section and connected to said second passageway and said fourthvertical section.

7. The invention set forth in claim 6 wherein said filters comprisestubular fabric filter bags suspended within said second and fourthvertical sections so that the air stream passing through said housingflows from the exterior of said bags to the interior of said bags andfine particulate material accumulates on the exterior surface thereof,and wherein the average porosity of the bags in said fourth verticalsection exceeds the average porosity of the bags in said second verticalsection.

1. A VACUUM LOADING OR CLEANING DEVICE COMPRISING: A MATERIAL RECEIVINGCHAMBER, SAID CHAMBER INCLUDING INLET MEANS AND OUTLET MEANS, VACUUMPUMP MEANS CONNECTED TO SAID CHAMBER OUTLET MEANS FOR CREATING A VACUUMIN SAID CHAMBER AND FOR DRAWING A HIGH VELOCITY AIR STREAM FROM SAIDCHAMBER INLET MEANS THROUGH SAID CHAMBER TO SAID CHAMBER OUTLET MEANS,FILTER MEANS INTERPOSED BETWEEN SAID CHAMBER AND SAID PUMP MEANS FORFILTERING FINE PARTICULATE MATERIAL FROM THE AIR STREAM PASSING FROMSAID CHAMBER TO SAID PUMP MEANS, SAID FILTER MEANS COMPRISING: A HOUSINGHAVING TWO INLET MEANS COUPLED WITH SAID CHAMBER OUTLED MEANS AND AHOUSING OUTLET MEANS COUPLED TO SAID VACUUM PUMP MEANS, AIR STREAMDIRECTING MEANS WITHIN SAID HOUSING DEFINING TWO AIR STREAM FLOW PATHSTHROUGH SAID HOUSING, ONE OF SAID FLOW PATHS CONNECTING ONE OF SAIDHOUSING INLET MEANS TO SAID HOUSING OUTLET MEANS AND THE OTHER OF SAIDFLOW PATHS CONNECTING THE OTHER OF SAID HOUSING INLET MEANS TO SAIDHOUSING OUTLET MEANS, FILTERS IN SAID HOUSING FOR FILTERING FINEPARTICULATE MATERIAL FROM THE AIR STREAM PASSING THROUGH SAID HOUSING,SAID FILTERS COMPRISING A FIRST AND A SECOND PORTION, SAID FIRST PORTIONAND SAID SECOND PORTION OF SAID FILTERS BEING ARRANGED IN SAID HOUSINGFOR FILTERING IN SERIES THE AIR STREAM PASSING THROUGH SAID FIRST FLOWPATH, SAID SECOND FLOW PATH BYPASSING SAID FIRST PORTION OF SAID FILTERSBUT INCLUDING SAID SECOND PORTION OF SAID FILTERS MEANS FOR SELECTIVELYCONTROLLING THE AIR FLOW FROM SAID CHAMBER OUTLET MEANS TO SAID HOUSINGOUTLET MEANS THROUGH ONE OF SAID FLOW PATHS.
 2. The invention set forthin claim 1 wherein said chamber outlet means comprise first and secondoutlets, said first outlet being connected to said one housing inletmeans and said second outlet being connected to the other of saidhousing inlet means, said chamber outlets being selectively closablewhereby air passing through said chamber may leave said chamber throughonly one of said chamber outlets.
 3. The invention set forth in claim 2further including first and second duct means coupling the interior ofsaid chamber to said first and second chamber outlets respectively, oneend of said first duct means being coupled to said first chamber outletand the other end of said first duct means being open to the upperportion of said chamber interior, and one end of said second duct meansbeing coupled to said second chamber outlet while the other end of saidsecond duct means is open to said chamber interior at a location thereinbelow said other end of said first duct means.
 4. The invention setforth in claim 3 wherein said second duct means is selectively closeableby a float valve means disposed at said other end of said second ductmeans, whereby said second duct means is closed to the passage of air ifliquid is being collected in said chamber and said liquid reaches apredetermined height in said chamber.
 5. The invention set forth inclaim 4 wherein said filters comprise tubular fabric filter bagssuspended within said housing so that the air stream passing throughsaid housing flows from the exterior of said bags to the interior ofsaid bags and fine particulate material accumulates on the exteriorsurface thereof.
 6. The invention set forth in claim 2 wherein said airstream directing means define: a first vertical section of said housing,said first section being divided into first and second verticalpassageways, the first one of said passageways connected to said oneinlet means and the second one of said passageways connected to saidother inlet means, a second vertical section adjacent said first sectionand containing said first portion of said filters, said second verticalsection being connected to said first passageway, a third verticalsection adjacent said second vertical section and defining a thirdpassageway leading from the upper portion of said second verticalsection to the lower portion of, a fourth vertical section adjacent saidthird vertical section and containing said second portion of saidfilters said fourth vertical section connected to said third passagewayand said housing outlet, and a first horizontal passageway passingthrough and beneath said second vertical section and connected to saidsecond passageway and said fourth vertical section.
 7. The invention setforth in claim 6 wherein said filters comprises tubular fabric filterbags suspended within said second and fourth vertical sections so thatthe air stream passing through said housing flows from the exterior ofsaid bags to the interior of said bags and fine particulate materialaccumulates on the exterior surface thereof, and wherein the averaGeporosity of the bags in said fourth vertical section exceeds the averageporosity of the bags in said second vertical section.